1. Field of the Invention
The present invention relates to a method of forming a patterned thin film. More particularly, the present invention provides a patterned thin film forming method useful for the manufacture of electronic devices such as storage devices, recording devices, microsensors, micromachines, and light-emitting devices. The method is capable of forming a patterned thin film on a substrate from such materials as ceramics and biopolymers, which have heretofore been difficult to form into patterned thin films by conventional vapor phase processes.
2. Discussion of Related Art
A large number of electronic ceramic devices are used as capacitors, resistors, varistors, etc. in compact electronic equipment such as those represented by portable telephones and mobile computers. It has been demanded that electronic ceramic devices should also be reduced in size and advance in function because of the progress of downsizing of electronic equipment.
Accordingly, many researchers in the world have extensively been proceeding with research and development making full use of lithography techniques to achieve finer ceramic thin film patterns constituting electronic ceramic devices to thereby realize higher integration. In these conventional processes, patterning is based on breakdown approach (see FIG. 9). That is, first, a desired thin film is formed on a substrate by a vapor phase method (partly by a liquid phase method). Thereafter, the thin film is patterned by etching.
For example, H. Krug reported a ceramic precursor thin-film pattern forming process utilizing a liquid phase (H. Krug, et. al., J. Non-crystalline Solids, 147and148, pp. 447-450, 1992). A photolithography process in which a precursor thin film formed on a substrate is exposed through a photomask is known. With this method, the resolution in the direction inside the thin film is limited by the wavelength of light used, because photolithography through a mask is used. Accordingly, the achievable patterning resolution is at the micrometer level at best. It is deemed extremely difficult to form a patterned thin film at the nanometer level.
Meanwhile, a technique based on built-up approach whereby molecules or ions are integrated on a substrate to form a nanometer-level pattern has been proposed, as opposed to the above-described breakdown approach. This is regarded as one of important assembling techniques, which is essential as an elemental technique in nanotechnology (see FIG. 10).
There are known thin-film pattern producing techniques using self-assembled monolayer (SAM) patterns as a template (B. C. Buker, et. al., Science, 264, pp. 48-55, 1994; Y. Xia, Ang. Chem. Int. Ed., 37, pp. 550-575, 1998). In these methods, SAM patterns of different properties are formed on a substrate. A nucleation and thin-film growth of precursor molecules preferentially occur on the SAM patterns owing to a difference in surface properties (hydrophilic nature and hydrophobic nature) in an aqueous solution. However, this method involves the problem that preprocessing for forming SAM patterns is complicated. In addition, there is a demand for improvements in the capability of controlling the deposition rate of precursor molecules at the nanometer level.
Methods of forming a patterned thin film under mild environmental conditions in a solution are known as xe2x80x9csoft solution processxe2x80x9d (Yoshimura, MRS Bulletin, 25, pp. 12-55, 2000 or xe2x80x9cbiomimetic processxe2x80x9d (Koumoto, Kagaku Souran 42, pp. 83-93, 1999). These methods are expected to provide an environmentally friendly, ecological manufacturing process that belongs to a new field of researches and is technologically simple and easy as well as low-cost. Accordingly, the expansion of fundamental techniques for the method is expected.
The present invention was made in view of the above-described circumstances.
An object of the present invention is to provide a novel patterned thin film forming method capable of realizing formation of nanometer-scale patterned thin films with high controllability by an easy and low-cost process, thereby overcoming the disadvantages of the prior art. First, the present invention provides a method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that an electric charge pattern is formed on the insulating substrate, and then the insulating substrate is dipped in the precursor solution to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
Secondly, the present invention provides a patterned thin film forming method characterized in that the insulating substrate is one selected from the group consisting of a silicon wafer, a glass, and a mica cleavage plane, each of which has a flat surface provided with a thermally oxidized film or an insulating dielectric film.
Thirdly, the present invention provides a patterned thin film forming method characterized in that the precursor solution containing a film-forming substance is one selected from the group consisting of a metal alkoxide, a metal acetyl acetate, and a metal carboxylate.
Fourthly, the present invention provides a patterned thin film forming method characterized in that a focused ion beam or a focused electron beam is applied to the surface of the insulating substrate to form an electric charge pattern in a non-contact manner.
Fifthly, the present invention provides a patterned thin film forming method characterized in that a metal probe or a microstamp is brought into contact with the surface of the insulating substrate to form an electric charge pattern.
Sixthly, the present invention provides a patterned thin film forming method characterized in that the rate of deposition of the film-forming substance on the electric charge pattern is adjusted by controlling the amount of electric charge carried by the electric charge pattern.
That is, the present invention provides the following patterned thin film forming methods.
(1) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that an electric charge pattern is formed on the insulating substrate, and then the insulating substrate is dipped in the precursor solution to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(2) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that an electric charge pattern is formed on the insulating substrate, which is one selected from the group consisting of a silicon wafer, a glass, and a mica cleavage plane, each of which has a flat surface provided with a thermally oxidized film or an insulating dielectric film, and then the insulating substrate is dipped in the precursor solution to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(3) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that an electric charge pattern is formed on the insulating substrate, and then the insulating substrate is dipped in the precursor solution containing the film-forming substance, which is one selected from the group consisting of a metal alkoxide, a metal acetyl acetate, and a metal carboxylate, to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(4) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that an electric charge pattern is formed on the insulating substrate, which is one selected from the group consisting of a silicon wafer, a glass, and a mica cleavage plane, each of which has a flat surface provided with a thermally oxidized film or an insulating dielectric film, and then the insulating substrate is dipped in the precursor solution containing the film-forming substance, which is one selected from the group consisting of a metal alkoxide, a metal acetyl acetate, and a metal carboxylate, to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(5) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that a focused ion beam or a focused electron beam is applied to the surface of the insulating substrate to form an electric charge pattern on the insulating substrate in a non-contact manner, and then the insulating substrate is dipped in the precursor solution to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(6) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that a focused ion beam or a focused electron beam is applied to the surface of the insulating substrate, which is one selected from the group consisting of a silicon wafer, a glass, and a mica cleavage plane, each of which has a flat surface provided with a thermally oxidized film or an insulating dielectric film, to form an electric charge pattern on the insulating substrate in a non-contact manner, and then the insulating substrate is dipped in the precursor solution to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(7) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that a focused ion beam or a focused electron beam is applied to the surface of the insulating substrate to form an electric charge pattern on the insulating substrate in a non-contact manner, and then the insulating substrate is dipped in the precursor solution containing the film-forming substance, which is one selected from the group consisting of a metal alkoxide, a metal acetyl acetate, and a metal carboxylate, to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(8) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that a focused ion beam or a focused electron beam is applied to the surface of the insulating substrate, which is one selected from the group consisting of a silicon wafer, a glass, and a mica cleavage plane, each of which has a flat surface provided with a thermally oxidized film or an insulating dielectric film, to form an electric charge pattern on the insulating substrate in a non-contact manner, and then the insulating substrate is dipped in the precursor solution containing the film-forming substance, which is one selected from the group consisting of a metal alkoxide, a metal acetyl acetate, and a metal carboxylate, to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(9) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that a metal probe or a microstamp is brought into contact with the surface of the insulating substrate to form an electric charge pattern on the insulating substrate, and then the insulating substrate is dipped in the precursor solution to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(10) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that a metal probe or a microstamp is brought into contact with the surface of the insulating substrate, which is one selected from the group consisting of a silicon wafer, a glass, and a mica cleavage plane, each of which has a flat surface provided with a thermally oxidized film or an insulating dielectric film, to form an electric charge pattern on the insulating substrate, and then the insulating substrate is dipped in the precursor solution to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(11) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that a metal probe or a microstamp is brought into contact with the surface of the insulating substrate to form an electric charge pattern on the insulating substrate, and then the insulating substrate is dipped in the precursor solution containing the film-forming substance, which is one selected from the group consisting of a metal alkoxide, a metal acetyl acetate, and a metal carboxylate, to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(12) A method of forming a patterned thin film on an insulating substrate in a precursor solution containing a film-forming substance, which is characterized in that a metal probe or a microstamp is brought into contact with the surface of the insulating substrate, which is one selected from the group consisting of a silicon wafer, a glass, and a mica cleavage plane, each of which has a flat surface provided with a thermally oxidized film or an insulating dielectric film, to form an electric charge pattern on the insulating substrate, and then the insulating substrate is dipped in the precursor solution containing the film-forming substance, which is one selected from the group consisting of a metal alkoxide, a metal acetyl acetate, and a metal carboxylate, to deposit the film-forming substance on the electric charge pattern formed on the insulating substrate.
(13) A method of forming a patterned thin film as stated in any of the above paragraphs (1) to (12), which is characterized in that the rate of deposition of the film-forming substance on the electric charge pattern is adjusted by controlling the amount of electric charge carried by the electric charge pattern.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.